1. Field of the Application
The present invention relates to channelization systems and methods for use in OFDM (orthogonal frequency division multiplexing) systems, such as OFDM wireless networks.
2. Background of the Disclosure
Conventional OFDM systems accommodate slow moving mobile stations in a manner that takes advantage of the fact that it is possible to track the fading in the frequency domain as well as the time domain. In order to take advantage of the slowly changing channel, sub-band scheduling is performed to assign a contiguous set of sub-carriers to each mobile station. In this case, each sub-band mobile station typically reports the carrier to interference ratio (CIR) for each sub-band or only the best sub-bands, where the number of bands to report is specified by the base station.
Conventional OFDM systems accommodate fast moving mobile stations as well. When a mobile station is moving too fast to perform channel sensitive scheduling, sub-carriers are assigned that are distributed over the entire bandwidth. In this case, the mobile station reports a full band CIR rather than a sub-band CIR.
The conventional approach to handling both slow moving mobile stations and fast moving mobile stations has been to have some transmission periods dedicated to slow moving mobile stations, and to have other transmission periods dedicated to fast moving mobile stations. An example of this is shown in FIG. 34 where the breakdown between resource allocation for slow moving mobile stations and fast moving stations is shown with frequency on the vertical access 10, and time on the horizontal axis 12. During some time intervals 14, the entire frequency band is used to support channels with distributed sub-carriers, while other time intervals 15 are used to support channels that are implemented using sub-bands.